A fuel cell has been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. In particular, the fuel cell has been identified as a potential alternative to the traditional internal-combustion engine used in modern vehicles.
One type of fuel cell is known as a proton exchange membrane (PEM) fuel cell. The PEM fuel cell typically includes three basic components: a cathode, an anode, and an electrolyte membrane. The cathode and anode typically include a finely divided catalyst, such as platinum, supported on carbon particles and mixed with an ionomer. The electrolyte membrane is sandwiched between the cathode and the anode to form a membrane-electrolyte-assembly (MEA). The MEA is often disposed between porous diffusion media (DM) which facilitate a delivery of gaseous reactants, typically hydrogen and oxygen, for an electrochemical fuel cell reaction. Individual fuel cells can be stacked together in series to form a fuel cell stack capable of powering a hydrogen fuel cell powered vehicle.
In order for hydrogen fuel cell powered vehicles to be a viable option for consumers, fueling stations must be capable of reliably dispensing gaseous hydrogen fuel. Dispensing systems for gaseous fueling typically installed at fueling stations are deemed operable after leak checks have been conducted. The leak checks during installation do not provide an opportunity to detect leakage that may occur during the operating lifetime of the dispensing systems, however. The installation leak checks also do not permit one to determine whether an interference leak during fueling of a particular vehicle is occurring. Generally, only major leaks due to line shear or hose damage, for example, are detected during the operating lifetime of the dispensing systems. Minor leakages at the vehicle interface are typically not detectable by fueling stations and customers, which results in an undesirable release of the gaseous hydrogen fuel to the environment.
A known system for dispensing hydrogen fuel is disclosed in U.S. Pat. Appl. Pub. No. 2005/0276749 to Noujima et al., the entire disclosure of which is hereby incorporated herein by reference. Noujima et al. describes a hydrogen fuel supplying machine generally made up of a fuel supply nozzle having an antenna for receiving data to be sent by a sensor net, which are flow rate sensors disposed downstream of a valve, a central processing unit for processing the transmitted data to determine an open degree of the valve, a memory for storing therein the sent data and the processing results of the central processing unit, and a valve control unit for controlling the valve in deference to the central processing unit's processing results. Noujima et al. additionally states that, by attaching the flow rate sensor to any part of a pipeline extending from the gaseous fuel stock unit up to the fuel supply nozzle, it becomes possible to rapidly detect gas leakage and flow abnormalities. However, the hydrogen fuel supplying machine and fuel supply nozzle of Noujima et al. cannot detect leakage that may occur at the interface of the fuel supply nozzle and a fuel cell powered vehicle during a fueling operation of the fuel cell powered vehicle.
There is a continuing need for a system and method for continuous leak detection during gaseous fueling of fuel cell powered vehicles.